theorem Th64:
  L is I_Lattice implies equivalence_wrt F is_reflexive_in the carrier of L
proof
  assume
A1: L is I_Lattice;
  let x be object;
  assume x in the carrier of L;
  then reconsider p = x as Element of L;
  p => p = Top L by A1,Th28;
  then p <=> p = Top L;
  then p <=> p in F by A1,Th11;
  hence thesis by Def11;
end;
